1. Field of the Invention
This invention relates to cameras, and more particularly to a camera that have a driving mechanism to perform plural operations of the camera using only one motor and that have a lens positioning control mechanism configured to bi-directionally control a lens position or other movable device using one driving direction of a driving force of the driving mechanism.
2. Discussion of the Background
Generally, in a camera a driving force from driving sources, such as motors, is transmitted to elements of the camera to perform different operations. For example, in a single focus camera, operations of (1) film feeding (2) focusing and (3) shutter releasing are performed by separate driving forces of the motors. Further, in a zoom camera where a relative positioning of lens groups is adjusted, operations of (1) zooming (2) film feeding (3) focusing and (4) shutter releasing are performed by the driving force of the motors.
In some cameras, in order to perform four operations, such as, for example, film winding and re-winding operations and lens forwarding and retracting operations, two separate motors are used, i.e., one motor for film feeding, and another motor for focusing. In these cases, each motor is used to perform a single operation, such as rotating the motor in one direction to drive a lens to an extended position, and rotating the motor in the other direction to retract the lens. In these conventional cameras a driving force of a motor is used in both rotational directions of the motor to move a member in a bidirectional direction, where bi-directional refers to a reciprocating, or forward and back motion. Moreover in this example, forward (e.g., clockwise) rotations of a first motor drive a film to be wound, reverse rotations of the first motor drive the film to be rewound, forward rotations of a second motor drive a lens to move from a home position to a focus position and reverse rotations of the second motor drive the lens to return from the focus position to the home position. Japanese Laid-Open Patent Publication No.5-181048/1993 describes an optical device in which a focus lens group is driven forward and backward (bi-directionally) for focusing purposes by switching forward and reverse rotations of one motor.
Moreover, in order to save cost and space of a motor, an alternate method is proposed to achieve the above-described four operations with a combination of one motor and one plunger, e.g., a solenoid plunger. Specifically, by switching on and off the plunger, the driving force of one motor is switched between two operations for each of forward and reverse rotations of the motor. With forward rotations of the motor, (1) when the plunger is switched on, a film is wound, and (3) when the plunger is switched off, a lens is moved from a home position to a focus position. With reverse rotations of the motor, (2) when the plunger is switched on, the film is rewound, and (4) when the plunger is switched off, the lens is returned from the focus position to the home position. Japanese Laid-Open Patent Publication No. 5-127236/1993 describes a camera in which a switching device is switched to be engaged with a zoom gear and a wind gear by two rotating directions of one motor. The switching device is held by a plunger while the switching device is engaged with the zoom gear or the wind gear. While the plunger is retracted, the switching device is free from the plunger and is driven to move from one gear to another gear so as to be engaged therewith.
As recognized by the present inventor, conventional devices and methods presume that controlling a moving member in two directions requires the use of two active members, such as a motor and a solenoid plunger. Accordingly, the use of the solenoid plunger, serves as a mechanical, binary device, that switches one circuit on, another circuit off depending on the state of the motor driving force. The solenoid plunger thus serves the mechanical equivalent of decision logic regarding which of the bi-directional moving devices will be controlled in both the forward direction and the reverse direction by the motor. However, using the forward and reverse directions of the motor in this way is not different than multiplexing the driving force made available from the motor.
The present inventor determined that including motors and other powered devices in a single camera increases the expense, weight, and complexity of the camera while lowering the mean time between failure of the device. The present inventor recognized that using the driving force of a motor in two directions can itself serve as a logic circuit for directing the mechanical energy of a single motor, albeit at less expense, weight and complexity than conventional devices with multiple motors.